Whatever you make of these arguments they all ignore an important political-economy consideration: a large Fed balance sheet makes for bad optics because of interest paid on excess reserve (IOER).

The figure below explains why. Using data from the Federal Reserve's H8 report, the figure shows the cash assets of "large domestically-chartered" banks and "foreign-related" banks. The figure reveals the cash assets of these two bank categories combined tracks excess reserves fairly closely. They are, in other words, the main holders of excess reserves and consequently the main recipients of the IOER payment.

Think about the implications: the banks that were bailed out during the crisis and the banks owned by foreigners are getting most of the IOER payment. This is a perfect storm of financial villains for both the political left and the right. That is why I agree with Ramesh Ponnuru that it politically naive to think the Fed can maintain a large balance.

And note, the bad optics will only look worse if the Fed's balance sheet does not shrink as interest rates go up. For the IOER payment will go up too. Imagine Fed Chair Janet Yellen having to explain to Congress the growing dollar payments going to these banks.

That is not to say it will be easy to shrink the Fed's balance sheet. There will be big challenges as I have noted elsewhere. But the bad optics do mean that it is likely the Fed will be forced to shrink its balance sheet.